- 1. Faculty of Sciences Department of Physical & Chemical Sciences January—May 2021 Prof. Sello Alfred Likuku Office Block 28 BSB 228: Introduction to Fluid Mechanics
- 2. March 13, 2021 2 1. Define internal, external, and open-channel flows. 2. Define incompressible flow and incompressible fluid. 3. Must the flow of a compressible fluid necessarily be treated as compressible? 4. What is the no-slip condition? What causes it? 5. What is forced flow? How does it differ from natural flow? 6. Is flow caused by winds forced or natural flow? 7. What is a boundary layer? What causes a boundary layer to develop? 8. What is the difference between the classical and the statistical approaches? 9. What is a steady-flow process? 10. Define stress, normal stress, shear stress, and pressure. 11. What are system, surroundings, and boundary? 12. When is a system a closed system, and when is it a control volume? 13. What is the difference between kg-mass and kg-force? Problems 1–13 are concept questions, and you are encouraged to answer them all 1-2 Tutorial Questions
- 3. March 13, 2021 3 14. A spherical balloon with a diameter of 6 m is filled with helium at 20°C and 200 kPa. Determine the mole number and the mass of the helium in the balloon.. [9.28 kmol.; 37.2 kg] 15. Determine the mass and the weight of the air contained in a room whose dimensions are 6 m × 6 m×8 m. Assume the density of the air is 1.16 kg/m3. [334.08 kg; 3277 N, based on g = 9.81 m/s2] 16. At 45° latitude, the gravitational acceleration as a function of elevation z above sea level is given by g = a – bz, where a = 9.81 m/s2 and b = 3.32×10–6 s–2. Determine the height above sea level where the weight of an object will decrease by 1 percent. [29,548 m] 17. A 68-kg astronaut took his bathroom scale (a spring scale) and a beam scale (compares masses) to the moon where the local gravity is g = 1.67 m/s2. Determine how much he will weigh (a) on the spring scale and (b) on the beam scale. [(a) 113.43 N; (b) 667.23 N] 18. The acceleration of high-speed aircraft is sometimes expressed in g’s (in multiples of the standard acceleration of gravity). Determine the net upward force, in N, that a 90-kg man would experience in an aircraft whose acceleration is 6 g’s. 19. The value of the gravitational acceleration g decreases with elevation from 9.81 m/s2 at sea level to 9.77 m/s2 at an altitude of 13,000 m, where large passenger planes cruise. Determine the percent reduction in the weight of an airplane cruising at 13,000 m relative to its weight at sea level. 20. A 5-kg rock is thrown upward with a force of 150 N at a location where the local gravitational acceleration is 9.79 m/s2. Determine the acceleration of the rock, in m/s2. 1-2 Tutorial Questions